Exploring allyl amine as a new structure II hydrate former: Guest inclusion behavior, structural characterization, and thermodynamic stability

In this study, we investigate the formation of structure II hydrate with a new hydrate-forming agent, allyl amine, in the presence of methane (CH₄) gas. Our findings confirm the guest inclusion behaviors, structural characteristics, and phase equilibria of a binary (allyl amine + CH₄) hydrate. The inclusion behaviors of allyl amine and methane in the binary (allyl amine + methane) hydrate are characterized by ¹³C solid-state nuclear magnetic resonance (NMR) spectroscopy. The crystal structure of the binary (allyl amine + CH₄) hydrate is identified as the cubic Fd-3m crystal structure, and the results of Rietveld analysis suggest the potential for possible guest–host interactions via hydrogen bonding. Furthermore, the phase equilibrium experiments assess the thermodynamic stability of the (allyl amine + CH₄) hydrate, comparing its conditions with pure CH₄ hydrate and other structure II hydrates. These results provide valuable insights into the fundamental understanding of complex nature of the host – guest inclusion chemistry.